The U.S. Food and Drug Administration approved the world’s first human clinical trial of a therapy involving embryonic stem cells, the biotechnology company behind the planned trial announced Friday.

California-based Geron Corporation has been given the green light to proceed with its trial on a therapy for patients with spinal-cord injury. The trial involves injecting a stem-cell treatment into patients with severe spinal cord injury with the hope that it would help damaged nerve cells regrow and eventually allow patients to regain movement.

Both opponents and proponents of embryonic stem cell research highlight the fact that the FDA had originally approved the study in January 2009 and the trial was scheduled to begin last summer. But Geron found that animals used in a preclinical study had developed small cysts that appeared with “a higher frequency” than other studies, resulting in the FDA delaying the trial from proceeding.

Even proponents of embryonic stem cell research raised concern about this trial, noting its history with animals.

Embryonic stem cell research is controversial because it requires the destruction of the embryo during the process of harvesting the stem cells. Many pro-life groups, therefore, argue it is unethical and equate the research with abortion because it destroys another potential life. They also argue that adult stem research is an alternative that is both ethical and has proven results.

“Despite the efforts that are made to deny it, science continues to show us that the embryo is a human being in the making,” said Elio Sgreccia, emeritus head of the Pontifical Academy for Life, on Radio Vatican.

However, proponents of the research method highlight that embryonic stem cells are highly versatile and can develop into any tissue in the body. They, therefore, hope it can be used to develop organs for transplant and help regrow damaged nerves.

Under President George W. Bush, federally funded embryonic stem cell research was highly restricted. He twice vetoed legislations that would expand federal funding for the research. But President Obama in 2009 repealed Bush’s order that prevented the National Institutes of Health from funding the research beyond the cell lines that existed at the time.

Obama allowed greater freedom and federal funds for scientists who want to research using embryonic stem cell research.

Geron’s therapy, if successful, has the potential to help Alzheimer’s disease and multiple sclerosis, among other health problems.

The company has not scheduled a date when the trial will begin, but it wants to start this year. Geron has spent 15 years and more than $150 million on this therapy treatment, according to the San Jose Mercury News.